1. Field of the Invention
This invention relates to an apparatus for perforating a workpiece having a horizontally positioned arm member that is pivotally connected to a press frame and is arranged to individually receive a series of tool holders that are interchangeably attached to the swing arm, and more particularly to a punching apparatus operable to provide vertical reciprocal movement of a punch tool only when the horizontal arm member and attached tool holder are located in punching position with respect to the press frame.
2. Description of the Prior Art
Conventional machines for perforating sheet metal include a worktable supported by the lower portion of a press frame with a ram punch positioned vertically above the worktable in the upper portion of the press frame. A suitable punching tool is positioned below the ram punch above the workpiece and is arranged to move vertically toward and away from a die which is rigidly supported in the table. Examples of conventional punching machines and tool supporting structures are illustrated in U.S. Pat. Nos. 3,225,636, 3,246,554, 3,269,241, 3,270,605, 3,405,581, 3,456,542 and 3,779,113.
U.S. Pat. No. 3,270,605 discloses a clamping mechanism by which the tool support is releasably engaged to the upper arm of the frame. By manually releasing a hand lever, a hook acting through a cam means is movable into and out of engagement with a support pin of the tool support. The clamping mechanism is integral with the upper arm of the machine frame and thus remains fixed relative thereto for detachably receiving the tool support.
A carriage assembly for supporting a tool support holder of a punching machine is illustrated and described in U.S. Pat. No. 3,405,581. The carriage is rotatably mounted by antifriction rollers on a pair of parallel spaced rails which are positioned parallel to the longitudinal axis of the frame upper arm portion. The tool support holder is releasably locked to the carriage assembly and movable therewith between an extended and retracted position in which the carriage travels horizontally on the rails in a front-to-rear direction relative to the upper arm portion.
In U.S. Pat. No. 3,456,542 horizontally and vertically acting clamps secure a detachable tool support to the press frame upper arm. The clamps are rigidly carried by the press frame upper arm and are manually operable to engage and release vertical pins disposed in slots of the tool support. The clamps pivotally support the tool support which is moved into and out of operating position on the upper arm. However, the clamps remain fixed on the upper arm as the tool support is pivoted relative to the clamps.
There is need for a punching apparatus that has a tool support releasably engaged to the upper arm of the press frame and also pivotally connected to the frame upper arm for moving the punch tool into and out of punching relation with respect to the ram and die to facilitate efficient and rapid exchange of the punch tool in the tool support and die in the worktable.